1. Field of the Invention
The present invention relates to a light guide panel in which the generation of dark portions in a light incidence area is reduced and a display device employing the same.
2. Description of the Related Art
In general, liquid crystal displays, which include the light receiving type flat displays used in laptop computers, desktop computers, LCD TVs, and mobile communication terminals, do not form images by emitting light by themselves but by selectively emitting illumination light radiated from an external source such as backlight units installed behind the liquid crystal displays.
Backlight units can be classified into direct light type backlight units and edge light type backlight units according to the arrangement of the light source. A direct light type backlight unit includes a plurality of lamps that are installed directly under a liquid crystal display and emit light directly onto a liquid crystal panel.
A direct light type backlight unit can be installed in a desired position on a broad surface and, thus, is appropriate for a large screen display device such as an LCD TV larger than 30 inches. An edge light type backlight unit is appropriate for small or medium sized displays like monitors or cell phones since the light source thereof is installed at a lateral side of a light guide panel.
FIG. 1 is a perspective view of a conventional edge light type backlight unit. Referring to FIG. 1, a light emitting device (LED) 10 installed at a side of a light guide panel (LGP) 20 emits light, and the emitted light is transferred to a liquid crystal panel via the LGP 20. A lower surface 15 of the LGP 20 is a reflection surface for advancing light toward the display panel. The light emitted from the LED 10 is converted into surface light by the LGP 20 and exits through an upper surface 17 of the LGP 20.
FIG. 2 illustrates the light from the LED 10 traveling through the LGP 20. Referring to FIG. 2, dark portions D having low brightness are created on the incident surface of the LGP 20 because of relatively little light arriving from the light source. FIG. 3 illustrates the light emitting efficiency according to the light emission angle of the LED 10. The light emitting efficiency of the LED 10 decreases from 0° to 90°. In other words, most of the light from the LED 10 is emitted forward, and thus the amount of light emitted laterally is relatively small. Accordingly, as illustrated in FIG. 2, the dark portions D, that is, areas where small quantities of light arrive from the LED 10, exist. The dark portions D cause irregular brightness and, thus, result in decreased display quality. Accordingly, an area within a distance d from the LED 10, where the dark portions D are created, is not included in a portion of the screen used for viewing. That is, the area away from the dark portions D is used as an effective screen 25. The area within the distance d from the LED 10 is unused and, thus, the miniaturization of the backlight unit may be difficult.